catena-Poly[[bis(1H-indole-5-carboxylato-κ2 O,O′)zinc(II)]-μ-4,4′-azobipyridine-κ2 N 1:N 1′]

The asymmetric unit of the title coordination polymer [Zn(C9H6NO2)2(C10H8N4)] n , consists of one ZnII cation, one bidentate 1H-indole-5-carboxylate (I5C) anion and half of a 4,4′-azobipyridine (Abpy) neutral ligand. The coordination polymer is stabilized by a combination of N—H⋯O and C—H⋯π interactions, which leads to the formation of wave-like two-dimensional coordination polymeric layers.

The asymmetric unit of the title coordination polymer [Zn(C 9 H 6 NO 2 ) 2 -(C 10 H 8 N 4 )] n , consists of one Zn II cation, one bidentate 1H-indole-5-carboxylate (I5C) anion and half of a 4,4 0 -azobipyridine (Abpy) neutral ligand. In the coordination polyhedron, the Zn II ion adopts a distorted octahedral geometry. The coordination polymer is stabilized by a combination of N-HÁ Á ÁO and C-HÁ Á Á interactions, which leads to the formation of wave-like two-dimensional coordination polymeric layers.

Structure description
The design of coordination polymers (CPs) and metal-organic frameworks (MOFs) is one of the most important fields in inorganic crystal engineering and material science because of their utility, functions and interesting architectures (Ying et al., 2015;Li et al., 2018). The self-assembly of metal-organic frameworks and coordination polymers is obtained by complexing metal ions with organic ligands (Li et al., 2018). In the field of storage and separation sciences, MOFs are a strong competitor for zeolites and carbon nanotubes (Naik et al., 2011;Cui et al., 2014). Several MOF structures with Zn II ions have recently been reported (Ying et al., 2015;Huang et al., 2015;Liu et al., 2017;Chen et al., 2020). In the present work, we report the crystal structure of a Zn II -containing coordination polymer constructed using 4,4 0 -azopyridine and indole-5-carboxylic acid.
The asymmetric unit consists of one Zn II cation, one bidentate 1H-indole-5carboxylate (I5C) anion and half of a 4,4 0 -azobipyridine (Abpy) neutral ligand. The other half of the Abpy ligand is generated by a centre of inversion (symmetry operation À 1 2 À x,  Fig. 2). Adjacent layers are held together by weak C-HÁ Á Á interactions between the C-H group of an Abpy ligand and the aromatic ring of an I5C anion (Table 1).
Cg is the centroid of the C2-C7 ring.

Figure 2
Polyhedral representation of the one-dimensional coordination polymer linked together by N-HÁ Á ÁO (blue dotted lines).

data-1
IUCrData ( where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.80 e Å −3 Δρ min = −0.31 e Å −3 Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. Refinement. H atoms bonded to C were positioned geometrically and refined using a riding model with C-H = 0.93 and with U iso (H) = 1.2 U eq (C). The H atom bonded to N was freely refined.